Draft: Bug 12: Add overload monitoring scripts
The scripts a) take data from Onionoo and prepare a JSON file with all the overloaded relays and bridges. b) load the JSON file and prepare a proper CSV output for plotting. c) plot various overload conditions.
This helps with overload analysis (see: network-health/team#66) as well.
Closes: #12 (closed), team#64 (closed).